Time series works very well on Cassandra. If anything, avoiding global-ordering hot spots is a Good Thing.

http://rubyscale.com/blog/2011/03/06/basic-time-series-with-...

http://www.datastax.com/dev/blog/advanced-time-series-with-c...

http://www.youtube.com/watch?v=F-fYqPu2ciQ&feature=youtu...